1. Field of the Invention
This invention relates to an apparatus having vacuum applying facilities and method of using vacuum to bend and/or shape one or more sheets, e.g. a pair of glass sheets to be laminated, and more particularly, this invention relates to the simultaneous shaping of a pair of glass sheets by a combination of gravity sag bending, press bending and negative air pressure.
2. Discussion of the Technology
The desire of automotive designers to have windshields with more complicated bends and deeper sags, and the requirement that the windshield conform to a predetermined surface profile over its entire extent, places demands on the glass fabricator to produce more difficult shaped glass parts with more stringent tolerances. Such complicated shapes are desired for vehicle styling purposes and for fuel economy, e.g. reduction of air friction. To achieve these objectives, the shape of the glass part is required to meet tight tolerances to enable the shaped glass sheets, e.g. shaped laminated windshields to be mounted in a curved mounting frame forming part of an automobile body to merge the windshield with the shape of the curved mounting.
U.S. patent application Ser. No. 10/706,884 filed on Nov. 12, 2003, in the names of James H. Schwartz et al. for “APPARATUS AND METHOD FOR BENDING GLASS SHEETS” discloses the use of a ring or outline mold having pressure applying facilities to shape glass sheets to complicated shapes by sag bending, press bending and static air pressure while minimizing marking of the glass sheets during the bending operation to shape the sheets. Although the mold arrangement disclosed in the above-mentioned patent application has the capabilities to shape one or more glass sheets to meet today's complicated shapes and optical standards, there are limitations. More particularly, the modification to the outline mold, and the equipment, to apply the static air pressure adds additional expense to the cost of the bending equipment.
As can be appreciated by those skilled in the art of shaping glass sheets, it would be advantageous to provide an inexpensive apparatus for, and method of, shaping one or more glass sheets to complicated shapes while minimizing marking and optical defects of the glass sheets during the bending operation to shape the sheet(s).